Quick Answer
Follow five steps in order: clean the sensor, remove reflective interference, adjust the sensor range, reset the unit, then check the wiring. Most cases get fixed in the first two steps.
Introduction
If you're asking why does my hand dryer keeps running even after your hands are gone, follow the steps below in the order given. Each step tests one possible cause, starting with the simplest. Complete each one fully before moving to the next.
Common Causes of a Hand Dryer That Won't Turn Off
How to Fix a Hand Dryer That Won't Stop Running
Step 1: Check for Dust Buildup
Turn off the power at the breaker, or unplug the unit.
Locate the sensor lens on the cover.
Wipe it gently with a soft, dry cloth. Do not use anything abrasive.
Restore power.
Place your hands under the dryer, then pull them away.
Count how long it takes to shut off. One to two seconds means the dust was the cause.
Step 2: Rule Out Reflective Surfaces and Ambient Light
Look at what surrounds the unit, including mirrors, countertops, and trash bins.
Move any loose reflective object away from the sensor's range.
Check whether sunlight hits the unit directly at certain times of day.
Block or shade the light source if it does.
Retest by placing your hands under the dryer and pulling away.
Step 3: Fix Sensor Calibration and Range
Locate the range dial near the sensor eye, often labeled R.
Turn off the power before adjusting it.
Turn the dial down by one small increment.
Restore power and test again.
Repeat in small increments until the shutoff time returns to one or two seconds.
Check the manufacturer guidelines for the recommended range at your mounting height.
Step 4: Reset the Unit
Locate the reset button near the cover screws or inside the housing.
Turn off the power.
Press and hold the reset button as directed by the manufacturer.
Restore power.
Test the unit again.
Step 5: Inspect Wiring and Electrical Components
Stop here and contact a licensed technician.
Ask the technician to test the wiring, control board, and power supply separately.
Request a report on which component caused the fault.
Use that report to decide between a repair and a full replacement.
For more diagnostic steps beyond wiring, see this hand dryer troubleshooting guide.
Choosing a More Reliable Touchless Unit
Look for a unit with adjustable sensor calibration built in, since this holds steady longer than fixed sensors. Compare options in our touchless hand dryers selection before you buy.
When to Replace Instead of Repair
Get a repair quote from your technician.
Compare it against the cost of a new unit.
Check part availability for your current model.
Choose replacement if parts are scarce or the quote exceeds half the cost of a new unit.
See our Commercial Hand Dryers page for current models.
How to Maintain a Commercial Hand Dryer Sensor
Clean the sensor lens weekly in high-traffic restrooms.
Check the air intake and HEPA filter monthly.
Log the date of each check.
Review the log quarterly to spot recurring issues early.
See our collection on energy-efficient hand dryers for lower-maintenance models.
Conclusions
Work through the five steps in order: clean the sensor, remove reflective interference, adjust the range, reset the unit, then check the wiring last. Most units get fixed in the first two steps.
FAQs
How do I check if humidity is causing the problem?
Test the unit right after sink use, then again after it's been dry a while, and compare the shutoff time.
How do I fix interference from a mirror or countertop?
Move loose reflective objects out of range, or adjust the sensor angle if the mirror is fixed in place.
How do I check for power fluctuation issues?
Have a technician test outlet voltage with a multimeter during both normal and problem periods.
How do I test if the shutoff delay is normal?
Time it with a stopwatch. One to two seconds is normal. Anything longer means starting at step one.
How do I estimate the added electricity cost?
Multiply the motor's wattage by the extra runtime, then apply your local electricity rate.
How do I confirm the sensor itself is the fault?
Test the wiring and control board first, since a new sensor won't fix a wiring issue.
How do I check a brand's sensor calibration quality?
Review the manufacturer's spec sheet for adjustable range settings and included calibration tools.
How do I check if installation caused the problem?
Measure the mounting height against the manufacturer guidelines, and check for reflective surfaces across from the unit.